The Ghost website itself doesn't ship with any trackers, and I didn't bother to set any up, so there's not much to disclose on that end. Here's Ghost's GDPR Compliance statement.
Mailgun does track—sort of loosely—whether people open each newsletter, but it's generally not terribly reliable and I don't actually check the numbers for anything beyond making sure that the emails aren't getting lost in the ether. You're welcome to use RSS if you'd prefer I not be able to track your email information, though.
If there's any other information like that available to me I frankly don't know how to access it. If you sign up for the email newsletter I'll have access to your email address and I think some vague location data (I can't figure out how to disable that), but I'm not going to do anything with it except send this newsletter, which is exactly what you signed up for so shouldn't be a surprise.